In this paper, we present the results of a study of the reduction of nickel formate with hydrazine hydrate using polyol (ethylene glycol, diethylene glycol, 1,2-propylene glycol, and 1,5-pentanediol) as a medium and provide a fairly simple method for preparation of nickel nanowires having the potential for high-volume production.
The reduction of nickel formate was carried out as follows.
In the case of nickel formate, the reduction reaction proceeds without adding alkaline reagents to the system which excludes the formation of nickel hydroxide as an intermediate and avoids contamination of the final product by them.
In order to determine the optimum temperature required for the reduction of nickel formate with hydrazine hydrate in ethylene glycol and to understand the influence of temperature, a series of experiments was carried out at reaction temperatures of 80, 100, 110, 120, 130, and 150[degrees]C and at a nickel formate to ethylene glycol weight ratio of 1: 100.
At 120[degrees] C, the reduction reaction proceeds slowly resulting in the formation of a mixture containing mostly metallic nickel with the impurity of the initial complex of nickel formate with hydrazine hydrate.
Effect of Nickel Formate Concentration on the Morphology of the Nickel Nanoparticles.
Initially, when nickel formate is dissolved in ethylene glycol, the formation of the nickel formate species solvated by ethylene glycol molecules occurs (1).
Since, at temperatures below 130[degrees]C, nickel nanowires grow from seeds initially formed on the crystals precipitated from the solution, we isolated the intermediate obtained by the addition of hydrazine hydrate to the solution of nickel formate in ethylene glycol at 100[degrees]C, first studying its morphology and composition and then the process of its reduction in ethylene glycol with hydrazine hydrate.
There could be a few reasons why such a shape is realized during the reduction of nickel formate by hydrazine hydrate in ethylene glycol.
Thus, it was shown that nickel nanoparticles resulting from the reduction of nickel formate in diethylene glycol, 1,2-propylene glycol, and 1,5-pentanediol do not possess a wire-like shape (Figure 6).
Nickel nanowires have been prepared in two simple ways: by reduction of both nickel formate and nickel hydrazine formate Ni[([N.sub.2][H.sub.4]).sub.2][(CHOO).sub.2] with hydrazine hydrate in ethylene glycol at 130[degrees]C without the use of other components such as additional capping agents.
Caption: FIGURE 1: SEM images of the samples obtained by reduction of nickel formate with hydrazine hydrate at temperatures of 100[degrees]C (a) and 110[degrees]C (b).